alt Hacker NewsI kind of doubt they would do this to be honest. Every near-copy of a message is going to have small differences in at least the envelope (not sure if encoding differences are also possible depending on the server), and possibly going to be under different guarantees or jurisdictions. And it would just take one mistake to screw things up and leak data from one person to another. All for saving a few gigabytes over an account's lifetime. Doesn't really seem worth it, does it?
That's why a base and a delta. Whereas PP was talking about general compression algorithm, my question was different.
In line with the original comment, I was asking about specialized "codecs" for gmail.
Humans do not read the same email many times. That makes it a good target for compression. I believe machines do read the same email many times, but that could be architected around.